Network Working Group B. Cheng
Internet-Draft Lincoln Laboratory
Intended status: Standards Track L. Berger, Ed.
Expires: May 3, 2018 LabN Consulting, L.L.C.
October 30, 2017
DLEP Multi-Hop Forwarding Extensiondraft-ietf-manet-dlep-multi-hop-extension-01
Abstract
This document defines an extension to the DLEP protocol that enables
the reporting and control of Multi-Hop Forwarding by DLEP capable
modems.
Status of This Memo
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This Internet-Draft will expire on May 3, 2018.
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Internet-Draft DLEP Multi-Hop Extension October 2017
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2. Extension Usage and Identification
The use of the Multi-Hop Forwarding Extension SHOULD be configurable.
To indicate that the extension is to be used, an implementation MUST
include the Multi-Hop Forwarding Extension Type Value in the
Extensions Supported Data Item. The Extensions Supported Data Item
is sent and processed according to [RFC8175].
The Multi-Hop Forwarding Extension Type Value is TBA1, see Section 5.
3. Extension Data Items
Three data items are defined by this extension. The Hop Count Data
Item is used by a modem to provide the number of network hops
traversed to reach a particular destination. The Hop Control Data
Item is used by a router to request that a modem alter connectivity
to a particular destination. The Suppress Forwarding Data Item is
used by a router to request that a modem disable multi-hop forwarding
on either a device or destination basis.
3.1. Hop Count
The Hop Count Data Item is used by a modem to indicate the number of
physical hops between the modem and a specific destination. In other
words, each hop represents a transmission and the number of hops is
equal to the number of transmissions required to go from a router
connected modem to the destination's connected modem. The minimum
number of hops is 1, which represents the router's locally connected
modem.
The data item also contains an indication of when a destination which
currently has a hop count of greater than one (1) could be made
direcly reachable by a modem, e.g., by re-aiming an antenna.
The Hop Count Data Item SHOULD be carried in the Destination Up,
Destination Update, Destination Announce Response, and Link
Characteristics Response Messages when the Hop Count to a destination
is greater than one (1).
A router receiving a Hop Count Data Item MAY use this information in
its forwarding and routing decisions, and specific use is out of
scope of this document. The absence of the Hop Count Data Item MUST
be interpreted by the router as a Hop Count value of one (1).
The format of the Hop Count Data Item is:
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Hop Count |P| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: TBA2
Length: 4
Hop Count:
An unsigned 8-bit integer indicating the number of network hops
required (i.e., number of times a packet will be transmitted) to
reach the destination indicated in the message. The special value
of 255 (0xFF) is used to indicate that the number of hops is an
unknown number greater than one (1). This field MUST contain a
value of at least one (1) if the associated destination is
reachable.
A value of zero (0) is used to indicated that processing of a Hop
Control action, see Section 3.2, has resulted in a destination no
longer being reachable. A zero value MUST NOT be used in any
message other then a Destination Announce Response Message.
P:
The P-bit indicates that a destination is potentially directly
reachable. When the P-bit is set, the router MAY request a direct
link to the associated destination using the Hop Control Data Item
described below.
Reserved:
MUST be set to zero by the sender (a modem) and ignored by the
receiver (a router).
3.2. Hop Control
The Hop Control Data Item is used by a router to request a change in
connectivity to a particular destination, or in multi-hop processing
on a device wide basis. A router can request multi-hop reachable
destination be changed to a single hop. A router can also indicate
that the modem terminate connectivity to a particular destination.
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Internet-Draft DLEP Multi-Hop Extension October 20173.2.1. Reset
The Reset Action requests that the default behavior be restored.
When received in a Session Update Message message, a modem SHOULD
clear all control actions that have previously been processed on a
device wide basis, and revert to its configured behavior. When
received in a Destination Announce Message, a modem SHOULD clear all
control actions that have previously been processed for the
destination indicated in the message.
3.2.2. Terminate
The Terminate Action is only valid on a per destination basis and
MUST NOT be sent in a Session Update Message message. It indicates
that the modem SHOULD attempt to terminate communication with the
destination identified in the message. This request has no impact
for multi-hop destinations and may fail even in a single hop case,
i.e. MAY result in the Hop Count to the destination not being
impacted by the processing of the request
3.2.3. Direct Connection
The Direct Connection is only valid on a per destination basis and
MUST NOT be sent in a Session Update Message message. It indicates
that the modem SHOULD attempt to establish a direct connection with
the destination identified in the message. This action SHOULD only
be sent for destinations for which the Hop Count is greater than 1
and has the P-Bit set in the previously received Hop Count Data Item.
Results of the request for the destination identified in the message
are provided as described above. If any other destination is
impacted in the processing of this action, the modem MUST send a
Destination Update Message for each impacted destination.
3.2.4. Suppress Forwarding
The Suppress Forwarding Action is used by a router to indicate to its
peer that multi-hop forwarding is to be suppressed. A router may
request that multi-hop forwarding may be suppressed on a device wide
or destination specific basis.
A modem which receives the Suppress Forwarding Data Item in a Session
Update Message MUST suppress multi-hop forwarding on a device wide
basis. Impact to destination hop counts are provided to the router
by the modem as described above.
A modem which receives the Suppress Forwarding Data Item in a
Destination Announce Message MUST suppress multi-hop forwarding for
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Internet-Draft DLEP Multi-Hop Extension October 2017
only the destination indicated in the message. Results are provided
as described above.
4. Security Considerations
The extension enables the reporting and control of forwarding
information by DLEP capable modems. The extension does not
inherently introduce any additional threats above those documented in
[RFC8175]. The approach taken to Security in that document applies
equally when running the extension defined in this document.
5. IANA Considerations
This document requests the assignment of 3 values by IANA. All
assignments are to registries defined by [RFC8175]. It also requests
creation of one new registry.
5.1. Extension Type Value
This document requests 1 new assignment to the DLEP Extensions
Registry named "Extension Type Values" in the range with the
"Specification Required" policy. The requested value is as follows:
+------+----------------------+
| Code | Description |
+------+----------------------+
| TBA1 | Multi-Hop Forwarding |
+------+----------------------+
Table 2: Requested Extension Type Value
5.2. Data Item Values
This document requests 2 new assignments to the DLEP Data Item
Registry named "Data Item Values" in the range with the
"Specification Required" policy. The requested values are as
follows:
+-----------+-------------+
| Type Code | Description |
+-----------+-------------+
| TBA2 | Hop Count |
| | |
| TBA3 | Hop Control |
+-----------+-------------+
Table 3: Requested Data Item Values
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